It's not strange or bad, just different. I always liked italicizing spell names the way you might italicize the title of a book -- it gave a sort of artistic feel to them. It makes them feel like they're the name of something, and in a more subtle way than something like capitalization would. When they're bold instead, they look less like names to me and more like keywords. Now that I think about it, putting them in bold affords the same advantage to them as it does to keywords: it makes them easier to spot when scanning through the reference.